1. Field of the Invention
The present invention relates to a turbine housing of a turbocharger.
2. Description of the Related Art
A turbocharger operates on the energy of high-temperature exhaust gas which can be, for example, at about 900.degree. C. A turbine housing is generally made of Ni-resist iron having high heat resistance. Ni-resist iron is austenite iron containing 20 to 40% by weight of Ni. Since Ni-resist iron is expensive, the unit price of the turbocharger is increased.
Ductile iron is known as a cheap and common material for a turbine housing. It is high Si-ferritic iron containing 3 to 4.5% by weight of Si. However, ductile iron has poor heat resistance as compared with Ni-resist iron. When ductile iron is used as a material for a turbine housing of a turbocharger, the surface of the ductile iron is oxidized and deteriorated by the heat of the high-temperature exhaust gas.